SUNOCO PIPELINE L.P.

Incident Narrative

ON FEBRUARY 15, 2021 AT APPROXIMATELY 8:20AM A LANDOWNER CALLED THE COMPANY CONTROL ROOM REPORTING A TANK OVERFLOW AT THE PUMP STATION IN SWEETWATER TEXAS. AT 8:27AM THE CONTROL ROOM CALLED OPERATIONS PERSONNEL TO INVESTIGATE. AT 9:46AM OPERATIONS PERSONNEL ARRIVED AT THE SWEETWATER PUMP STATION AND CONFIRMED THE TANK OVERFLOW AND SHUT THE TANK SHELL VALVE TO STOP THE OVERFILL. THE OPERATIONS PERSONNEL DETERMINED THE RELEASE WAS GREATER THAN 5 GALLONS AND TX RRC WAS NOTIFIED (INCIDENT 2355). AT APPROXIMATELY 10:50 AM IT WAS DETERMINED THAT THE RELEASE WOULD MEET TELEPHONIC REPORTING CRITERIA AND A CALL WAS PLACED TO THE NRC AT 11:32AM (NRC #1298034). UPON FURTHER INVESTIGATION, IT WAS DETERMINED THAT THE PRODUCT HAD MIGRATED OFF THE STATION PROPERTY ONTO A AN ADJACENT PROPERTY. A CLEAN UP COMPANY WAS DISPATCHED AND BEGAN CLEANUP OF FREE PRODUCT AND CONTAMINATED SOIL REMEDIATION. ON FEBRUARY 16TH AT 5:35PM A 48HR UPDATE WAS PLACED TO THE NRC (NRC #1298168). THE CAUSE OF THE OVERFILL WAS DETERMINED TO BE THE RELIEF VALVE FROM THE PIPELINE FAILING OPEN WHICH ALLOWED THE TANK TO CONTINUOUSLY FILL. THIS RELIEF VALVE IS ACTIVATED ON PRESSURE AND UNDER NORMAL OPERATION HELD CLOSED BY NITROGEN PRESSURE UNTIL THE RELIEF SETPOINT IS REACHED. THE AMBIENT TEMPERATURES THAT DAY WERE SUBFREEZING AND THERE WAS A POWER OUTAGE. THE POWER OUTAGE ALLOWED THE NITROGEN TANK HEATERS TO FAIL WHICH THEN CAUSED THE NITROGEN TO LEAK OUT OF THE RELIEF VALVE ALLOWING IT TO FAIL OPEN. AT THE TIME, THE PIPELINE WAS NOT IN OPERATION BUT WAS HOLDING APPROXIMATELY 189 PSI OF STATIC PRESSURE. DUE TO THE RELIEF VALVE FAILING OPEN THE STATIC PRESSURE ON THE PIPELINE BLED OFF THROUGH THE RELIEF VALVE AND CAUSED THE TANK TO OVERFILL. 11/04/2024 - UPDATED BY PHMSA PER OPERATOR APPROVAL.